PROJECT SUMMARY/ABSTRACT A fundamental gap exists in evidence regarding the safety and efficacy of service dogs for military veterans with posttraumatic stress disorder (PTSD) and their spouses. Continued existence of this gap represents an important problem, because until it is filled, this animal-assisted intervention strategy will continue to be minimized as an unsupported and potentially unsound practice. Although current psychosocial rehabilitation strategies for military veterans with PTSD are effective for some individuals, they have relatively high dropout numbers and significant non-response rates. As a result, many veterans are increasingly seeking complementary interventions. A critical need exists to establish proof-of-concept for the efficacy of service dogs not only for veterans but also for their spouses, who also suffer from substantial psychological distress and live in the home with the service dogs. The long-term research goal is to evaluate the safety and efficacy of service dogs as a complementary intervention to enhance biopsychosocial functioning in special populations. The overall objective is to conduct a methodolog- ically rigorous, randomized controlled trial to quantify the therapeutic efficacy of service dogs on clinically-im- portant outcomes. The central hypothesis is that military veterans with PTSD who are provided service dogs will experience reduced PTSD symptoms related to socio-emotional functioning (social participation, mood) and arousal modulation (hyper-arousal, sleep disturbance). It is further hypothesized that spouses will experience similar outcomes to ameliorate their psychological distress and reduce their caregiver burden. Guided by strong preliminary data, these hypotheses will be tested by pursing three specific aims: (1) quantify the therapeutic efficacy of service dogs for socio-emotional functioning, (2) quantify the therapeutic efficacy of service dogs for arousal modulation, and (3) quantify the canine characteristics and human-animal interactions that moderate outcomes. Assessments will consist of ecological momentary assessment, objective physiological assessment, blinded clinician ratings, standardized surveys, and behavioral observation. Measures will assess the veterans, spouses, and canines. The approach is innovative because it departs from the status quo by applying gold- standard randomized controlled trial methodology to evaluate efficacy, enlisting novel ecological momentary assessment methodology to examine human-animal interactions that may moderate change, and collecting ob- jective physiological data to evaluate potential biological pathways, or mechanisms, by which service dogs elicit change. The proposed project is significant because it tests an increasingly used but poorly tested complemen- tary intervention that has the potential to address an important rehabilitation problem for military veterans with PTSD and their spouses. Ultimately, such knowledge has the potential to provide a much-needed evidence base for clinical care involving human-animal interaction. It will enable health care providers, veterans, and their fam- ilies to know what to expect from service dogs, as well as the canine, human, and interaction characteristics that moderate change to begin to determine for whom this service is effective and under what conditions.